Saccharin derivatives

ABSTRACT

Saccharin derivatives of the formula I ##STR1## where the substituents have the following meanings: L and M are hydrogen, C 1  -C 4  -alkyl, C 1  -C 4  -alkoxy, C 1  -C 4  -alkylthio, chlorine, cyano, methylsulfonyl, nitro or trifluoromethyl; 
     Z is hydrogen, C 1  -C 4  -alkyl, C 3  -C 8  -cycloalkyl, C 3  -C 6  -alkenyl, C 3  -C 5  -alkynyl, C 1  -C 4  -acyl, benzyl or phenyl, the phenyl rings being unsubstituted or substituted by halogen or C 1  -C 4  -alkyl; 
     R 1  is cyclopropyl, 1-methylcyclopropyl, 1-methylthiocyclopropyl or tert-butyl; 
     and agriculturally customary salts of the compounds I are described.

This application is a 371 of PCT/EP95/02977 filed Jul. 27, 1995.

The present invention relates to saccharin derivatives of the formula I ##STR2## where the substituents have the following meanings: L and M are hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -alkylthio, chlorine, cyano, methylsulfonyl, nitro or trifluoromethyl;

Z is hydrogen, C₁ -C₄ -alkyl, C₃ -C₈ -cycloalkyl, C₃ -C₆ -alkenyl, C₃ -C₅ -alkynyl, C₁ -C₄ -acyl, benzyl or phenyl, the phenyl rings being unsubstituted or substituted by halogen or C₁ -C₄ -alkyl;

R¹ is cyclopropyl, 1-methylcyclopropyl, 1-methylthiocyclopropyl or tert-butyl;

and agriculturally customary salts of the compounds I.

The invention further relates to herbicidal compositions containing the compounds I, and methods of controlling undesired plant growth using the saccharin derivatives I.

Saccharin derivatives having herbicidal action cannot be inferred from the prior art. However, unsubstituted saccharin (o-sulfobenzimide, ie. L, M, Q and Z in formula I=H) has been known as a synthetic sweetener for a long time. 4-Hydroxysaccharin is further known as a sweetener (German Offenlegungsschrift 3 607 343). The use of saccharin derivatives in pest control is also known, eg. JP publication 72/00419, 73/35457 (fungicides) and in pharmacy, eg. EP-A 594 257 and literature references mentioned therein.

Heterocyclic compounds having a sulfonamide-containing ring have been disclosed as herbicides, a typical representative which can be mentioned here being bentazone ##STR3##

It is an object of the present invention to make available novel herbicides having a basic structure which was hitherto unknown for this indication. We have found that this object is achieved by the compounds I defined at the outset.

Compounds of the formula I are obtained by acylating the magnesium enolate A2 of a cyano ketone of the formula A1 ##STR4## with a saccharincarbonyl chloride of the formula III to give the enolized compound I.1. ##STR5##

In the abovementioned formulae, L and M have the meaning given at the outset and Z is hydrogen, C₁ -C₄ -alkyl, C₃ -C₈ -cycloalkyl, C₃ -C₆ -alkenyl, C₃ -C₅ -alkynyl, C₁ -C₄ -acyl or benzyl or phenyl which is unsubstituted or substituted by halogen or C₁ -C₄ -alkyl.

The first step of the reaction sequence is carried out by treating a methanolic solution of a cyano ketone of the formula A1 with magnesium and a small amount of CCl₄ and allowing this to react to give the magnesium enolate. Analogous C acylations of cyano ketones are described eg. in EP-A 496 630 and EP-A 496 631.

After removing the methanol, the resulting magnesium enolate of the formula A2 is dissolved in toluene or acetonitrile, acetonitrile being preferred, and then the amount of the acid chloride of the formula III equivalent to A1 is added dropwise as an acetonitrile solution. After stirring at from 25° C. to 50° C. for 1-16 hours, the reaction is complete. For working up, it is concentrated under reduced pressure, the residue which remains is taken up in a solvent such as ethyl acetate or methylene chloride and washed with 10 percent HCl to decompose the magnesium salt. After washing the organic phase with water, it is dried with a drying agent such as sodium sulfate and concentrated. The product. is precipitated from the residue which remains by rubbing with a hydrocarbon such as petroleum ether, cyclohexane or n-pentane.

The cyano ketones of the formula A1 used as starting materials are generally known compounds. They can be obtained, for example, by reaction of cyanoacetic acid with butyllithium and then with an acid chloride R¹ --COCl.

The acid chlorides R¹ --COCl are obtained in a manner known per se from the corresponding carboxylic acids R¹ -COOH by reaction with thionyl chloride. The carboxylic acids R¹ -COOH are compounds which are known from the literature: pivalic acid and cyclopropanecarboxylic acid are commercially available compounds. 1-Methylcyclopropanecarboxylic acid is obtained either by hydrolysis of the commercially available ethyl ester or in a known manner by methylation of lithium α-lithiocyclopropanecarboxylate Warner+Le, JOC 47, (1982), 893!. 1-Methylthiocyclopropanecarboxylic acid is obtained in a known manner from 1-methylthiocyclopropanecarbonitrile, which can in turn be prepared from methylmercaptoacetonitrile and ethylene dibromide in the presence of sodium amide German Offenlegungsschrift 21 20 908=CA 76: 72099!.

The starting substances of the formula III ##STR6## are prepared in a manner known per se by reaction of the saccharincarboxylic acids II ##STR7## with thionyl chloride.

Saccharincarboxylic acids II are known in some cases (4-COOH: Zincke, Liebigs Ann. 427 (1922) 231, 5-COOH: Jacobsen, Chem. Ber. 13 (1880), 1554, 6-COOH: Weber, Chem. Ber. 25 (1892), 1740). Further, the preparation of 4-chlorosaccharin-5-carboxylic acid is described in German Offenlegungsschrift 36 07 343.

Saccharincarboxylic acids can also be obtained by reacting corresponding bromo- or iodo-substituted saccharin derivatives of the formula A3 ##STR8## where L, M and Z have the abovementioned meanings, or if Z≠H compounds of the formula A4 ##STR9## with carbon monoxide and water or a C₁ -C₆ -alcohol at elevated pressure in the presence of a palladium, nickel, cobalt or rhodium transition metal catalyst and a base.

If, for example, L is methyl and M and Z are hydrogen, the reaction sequence can be shown as follows: ##STR10##

The catalysts nickel, cobalt, rhodium and in particular palladium can be present in metallic form or in the form of customary salts, such as in the form of halogen compounds, eg. PdCl₂, RhCl₃.H₂ O, acetates, eg. Pd(OAc)₂, cyanides etc. in the known valency states. Metal complexes with tertiary phosphines, metal alkylcarbonyls, metal carbonyls, eg. CO₂ (CO)₈, Ni(CO)₄, metal carbonyl complexes with tertiary phosphines; eg. (PPh₃)₂ Ni(CO)₂, or transition metal salts complexed with tertiary phosphines can further be present. The last-mentioned embodiment is particularly preferred in the case of palladium as a catalyst. The nature of the phosphine ligands here is widely variable. For example, they can be represented by the following formulae: ##STR11## where n is the numbers 1, 2, 3 or 4 and the radicals R⁷ to R¹³ are low-molecular weight alkyl, eg. C₁ -C₆ -alkyl, aryl or C₁ -C₄ -alkylaryl, eg. benzyl, phenethyl or aryloxy. Aryl is eg. naphthyl, anthryl and preferably unsubstituted or substituted phenyl, it only being necessary with respect to the substituents to take into account their inertness to the carboxylation reaction, otherwise they can be widely varied and include all inert C-organic radicals such as C₁ -C₆ -alkyl radicals, eg. methyl, carboxyl radicals such as COOH, COOM (M is eg. an alkali metal, alkaline earth metal or ammonium salt), or C-organic radicals bonded via oxygen, such as C₁ -C₆ -alkoxy radicals.

The preparation of the phosphine complexes can be carried out in a manner known per se, eg. as described in the documents mentioned at the outset. For example, commercially available metal salts such as PdCl₂ or Pd(OCOCH₃)₂ are used as starting materials and the phosphine, eg. P(C₆ H₅)₃, P(n-C₄ H₉)₃, PCH₃ (C₆ H₅)₂ or 1,2-bis(diphenylphosphino)ethane is added.

The amount of phosphine, based on the transition metal, is customarily from 0 to 20, in particular from 0.1 to 10, mol equivalents, particularly preferably from 1 to 5 mol equivalents.

The amount of transition metal is not critical. For cost reasons, of course, rather a small amount, eg. from 0.1 to 10 mol %, in particular from 1 to 5 mol %, based on the starting substance A3 or A4, will be used.

Reaction with carbon monoxide and at least equimolar amounts of water, based on the starting substances A3 or A4, is carried out to prepare the saccharincarboxylic acids. The reaction component water or C₁ -C₆ -alkyl-OH can simultaneously also be used as a solvent, ie. the maximum amount is not critical.

However, it can also be advantageous, depending on the nature of the starting substances and the catalysts used, to use another inert solvent or the base used for the carboxylation as a solvent instead of the reaction component.

Suitable inert solvents for carboxylation reactions are customary solvents such as hydrocarbons, eg. toluene, xylene, hexane, pentane, cyclohexane, ethers, eg. methyl tert-butyl ether, tetrahydrofuran, dioxane, dimethoxyethane, substituted amides such as dimethylformamide, persubstituted ureas such as tetra-C₁ -C₄ -alkylureas, or nitriles such as benzonitrile or acetonitrile.

In a preferred embodiment of the process, one of the reaction components, in particular the base, is used in an excess such that no additional solvent is necessary.

Bases suitable for the process are all inert bases which are able to bind the hydrogen iodide or hydrogen bromide liberated in the reaction. Examples which can be mentioned here are tertiary amines such as triethylamine, cyclic amines such as N-methylpiperidine or N,N'-dimethylpiperazine, pyridine, alkali metal or alkaline earth metal hydroxides, carbonates or hydrogen carbonates, or tetraalkyl-substituted urea derivatives such as tetra-C₁ -C₄ -alkylurea, eg. tetramethylurea.

The amount of base is not critical, 1 to 10, in particular 1 to 5, mol customarily being used. When the base is simultaneously used as a solvent, as a rule the amount is proportioned such that the reaction components are dissolved, unnecessarily high excesses being avoided for reasons of practicability in order to save costs, to be able to employ small reaction vessels and to guarantee maximum contact of the reaction components.

During the reaction, the carbon monoxide pressure is adjusted such that an excess of CO, based on A3 or A4, is always present. Preferably, the carbon monoxide pressure at room temperature is from 1 to 250 bar, in particular from 5 to 150 bar, of CO. At different temperatures, the pressure is correspondingly higher or lower.

As a rule, the carbonylation is carried out continuously or batchwise at from 20° to 250° C., in particular at from 30° to 150° C. In the case of batchwise operation, carbon monoxide is expediently injected into the reaction mixture continuously to maintain a constant pressure.

The products are isolated from the resulting reaction mixture in a customary manner, eg. by distillation.

The starting substances A3 and A4 required for the reaction are known or can be prepared in a manner known per se. They can be obtained either by permanganate oxidation of iodo-substituted 2-methylbenzenesulfonamides or from aminosaccharides by Sandmeyer reaction. Aminosaccharins are obtained according to known methods by reduction of nitrosaccharides which, in turn, are either known (Kastle, Amer. Chem. Journal 11 (1889), 184 or DRP 551423 (1930)) or are synthesized from suitable nitrobenzene derivatives (Liebigs Ann. 669 (1963), 85) or benzenesulfonamides in a manner known from the literature.

Moreover, they can be obtained in a similar manner to the preparation procedures of Examples 1 to 12.

With respect to the intended use, saccharin derivatives of the formula I are preferred where the radicals L and M are hydrogen, methyl, methoxy, methylthio, chlorine, cyano, methylsulfonyl, nitro or trifluoromethyl.

In formula I, R¹ is particularly preferably cyclopropyl.

The radical Z is particularly preferably one of the C-organic radicals mentioned, in particular methyl, ethyl, acetyl, phenyl or propargyl.

Particularly preferred active compounds can be taken from Table 1.

The groups mentioned in Table 1 for a substituent are additionally considered per se, independently of the specific combination with other substituents in which they are mentioned, to be a particularly preferred definition of the substituents concerned.

The compounds I can be present in the form of their agriculturally utilizable salts, the nature of the salt in general not mattering. Customarily, the salts of those bases which do not adversely affect the herbicidal action of I are suitable.

Suitable basic salts are particularly those of the alkali metals, preferably the sodium and potassium salts, those of the alkaline earth metals, preferably calcium, magnesium and barium salts and those of the transition metals, preferably manganese, copper, zinc and iron salts as well as the ammonium salts, which can carry one to three C₁ -C₄ -alkyl or hydroxy-C₁ -C₄ -alkyl substituents and/or a phenyl or benzyl substituent, preferably diisopropylammonium, tetramethylammonium, tetrabutylammonium, trimethylbenzylammonium and trimethyl-(2-hydroxyethyl)ammonium salts, the phosphonium salts, the sulfonium salts, preferably tri(C₁ -C₄)-alkylsulfonium salts, and the sulfoxonium salts, preferably tri(C₁ -C₄)-alkylsulfoxonium salts.

The compounds I, the herbicidal compositions containing them and their environmentally tolerable salts of, for example, alkali metals, alkaline earth metals or ammonia and amines or the herbicidal compositions containing them can control broad-leaved weeds and grass weeds highly effectively in crops such as wheat, rice, maize, soybeans and cotton without noticeably damaging the crop plants. This effect occurs especially at low application rates.

Taking into account the versatility of the application methods, the compounds I or compositions containing them can also be employed in a further number of crop plants for the elimination of undesired plants. Examples of suitable crops are the following:

Alliumcepa, Ananas comosus, Arachis hypogaea, Asparagus officinalis, Beta vulgaris spp. altissima, Beta vulgaris spp. rapa, Brassica napus var. napus, Brassica napus var. napobrassica, Brassica rapa var. silvestris, Camellia sinensis, Carthamus tinctorius, Carya illinoinensis, Citrus limon, Citrus sinensis, Coffea arabica (Coffea canephora, Coffea liberica), Cucumis sativus, Cynodon dactylon, Daucus carota, Elaeis guineensis, Fragaria yesca, Glycine max, Gossypium hirsutum, (Gossypium arboreum, Gossypium herbaceum, Gossypium vitifolium), Helianthus annuus, Hevea brasiliensis, Hordeum vulgare, Humulus lupulus, Ipomoea batatas, Juglans regia, Lens culinaris, Linum usitatissimum, Lycopersicon lycopersicum, Malus spp., Manihot esculenta, Medicago sativa, Musa spp., Nicotiana tabacum (N. rustica), Olea europaea, Oryza satira, Phaseolus lunatus, Phaseolus vulgaris, Picea abies, Pinus spp., Pisum sativum, Prunus avium, Prunus persica, Pyrus communis, Ribes sylvestre, Ricinus communis, Saccharum officinarum, Secale cereale, Solanum tuberosum, Sorghum bicolor (S. vulgare), Theobroma cacao, Trifolium pratense, Triticum aestivum, Triticum durum, Vicia faba, Vitis vinifera, Zea mays.

Moreover, the compounds I can also be employed in crops which have been made largely resistant to the action of I or other herbicides by breeding and/or by means of genetic engineering methods.

The application of the herbicidal compositions or of the active compounds can be carried out preemergence or postemergence. If the active compounds are less tolerable for certain crop plants, application techniques can be used in which the herbicidal compositions are sprayed with the aid of the spray equipment such that the leaves of the sensitive crop plants are not affected if possible, while the active compounds reach the leaves of undesired plants growing under them or the uncovered soil surface (post-directed, lay-by).

The compounds I or the herbicidal compositions containing them can be applied by spraying, atomizing, dusting, scattering or watering in the form of directly sprayable aqueous solutions, powders, suspensions, even high-percentage aqueous, oily or other suspensions or dispersions, emulsions, oil dispersions, pastes, dusting compositions, scattering compositions or granules. The application forms depend on the intended uses; if possible they should in each case guarantee the finest dispersion of the active compounds according to the invention.

Suitable inert auxiliaries for the preparation of directly sprayable solutions, emulsions, pastes or oil dispersions are essentially: mineral oil fractions of medium to high boiling point such as kerosene or diesel oil, further coal tar oils and oils of vegetable or animal origin, aliphatic, cyclic and aromatic hydrocarbons, eg. paraffins, tetrahydronaphthalene, alkylated naphthalenes or their derivatives, alkylated benzenes and their derivatives, alcohols such as methanol, ethanol, propanol, butanol and cyclohexanol, ketones such as cyclohexanone or strongly polar solvents, eg. amines such as N-methylpyrrolidone, or water.

Aqueous application forms can be prepared from emulsion concentrates, suspensions, pastes, wettable powders or water-dispersable granules by addition of water. To prepare emulsions, pastes or oil dispersions, the substances can be homogenized in water, as such or dissolved in an oil or solvent, by means of wetting agents, adhesives, dispersants or emulsifiers. However, concentrates consisting of active substance, wetting agent, adhesive, dispersant or emulsifier and possibly solvents or oil which are suitable for dilution with water can also be prepared.

Suitable surface-active substances are the alkali metal, alkaline earth metal or ammonium salts of aromatic sulfonic acids, eg. lignosulfonic, phenolsulfonic, naphthalenesulfonic and dibutylnaphthalenesulfonic acid, as well as of fatty acids, alkyl- and alkylarylsulfonates, alkyl-, lauryl ether and fatty alcohol sulfates, and also salts of sulfated hexa-, hepta- and octadecanols as well as of fatty alcohol glycol ethers, condensation products of sulfonated naphthalene and its derivatives with formaldehyde, condensation products of naphthalene or of the naphthalenesulfonic acids with phenol and formaldehyde, polyoxyethylene octyl phenol ethers, ethoxylated isooctyl-, octyl- or nonylphenol, alkylphenyl or tributylphenylpolyglycol ethers, alkylaryl polyether alcohols, isotridecyl alcohol, fatty alcohol-ethylene oxide condensates, ethoxylated castor oil, polyoxyethylene alkyl ethers or polyoxypropylene alkyl ethers, lauryl alcohol polyglycol ether acetate, sorbitol esters, lignin-sulfite waste liquors or methylcellulose.

Powder, scattering and dusting compositions can be prepared by mixing or joint grinding of the active substances with a solid carrier.

Granules, eg. coated, impregnated and homogeneous granules can be prepared by binding of the active compounds to solid carriers. Solid carriers are mineral earths such as silicic acids, silica gels, silicates, talc, kaolin, limestone, lime, chalk, bole, loews, clay, dolomite, diatomaceous earth, calcium sulfate and magnesium sulfate, magnesium oxide, ground synthetic materials, fertilizers, such as ammonium sulfate, ammonium phosphate, ammonium nitrate, ureas and vegetable products such as cereal flour, tree bark meal, wood meal and nutshell meal, cellulose powder or other solid carriers.

In general, the formulations contain from 0.01 to 95% by weight, preferably from 0.5 to 90% by weight, of active compound. The active compounds are employed here in a purity of from 90% to 100%, preferably from 95% to 100% (according to NMR spectrum). The compounds I according to the invention can be formulated, for example, as follows:

I. 20 parts by weight of the compound 1.03 are dissolved in a mixture which consists of 80 parts by weight of alkylated benzene, 10 parts by weight of the addition product of from 8 to 10 mol of ethylene oxide to 1 mol of oleic acid N-monoethanolamide, 5 parts by weight of calcium salt of dodecylbenzenesulfonic acid and 5 parts by weight of the addition product of 40 mol of ethylene oxide to 1 mol of castor oil. By pouring out the solution and finely dispersing it in 100,000 parts by weight of water, an aqueous dispersion is obtained which contains 0.02% by weight of the active compound.

II. 20 parts by weight of the compound 1.03 are dissolved in a mixture which consists of 40 parts by weight of cyclohexanone, 30 parts by weight of isobutanol, 20 parts by weight of the addition product of 7 mol of ethylene oxide to 1 mol of isooctylphenol and 10 parts by weight of the addition product of 40 mol of ethylene oxide to 1 mol of castor oil. By pouring the solution into and finely dispersing it in 100,000 parts by weight of water, an aqueous dispersion is obtained which contains 0.02% by weight of the active compound.

III. 20 parts by weight of the active compound 1.03 are dissolved in a mixture which consists of 25 parts by weight of cyclohexanone, 65 parts by weight of a mineral oil fraction of boiling point from 210° to 280° C. and 10 parts by weight of the addition product of 40 mol of ethylene oxide to 1 mol of castor oil. By pouring the solution into and finely dispersing it in 100,000 parts by weight of water, an aqueous dispersion is obtained which contains 0.02% by weight of the active compound.

IV. 20 parts by weight of the active compound 1.03 are thoroughly mixed with 3 parts by weight of the sodium salt of diisobutylnaphthalene-α-sulfonic acid, 17 parts by weight of the sodium salt of a lignosulfonic acid from a sulfite waste liquor and 60 parts by weight of powdered silica gel and ground in a hammer mill. By finely dispersing the mixture in 20,000 parts by weight of water, a spray mixture is obtained which contains 0.1% by weight of the active compound.

V. 3 parts by weight of the active compound 1.03 are mixed with 97 parts by weight of finely divided kaolin: in this way, a dusting composition is obtained which contains 3% by weight of the active compound.

VI. 20 parts by weight of the active compound 1.03 are intimately mixed with 2 parts by weight of calcium salt of dodecylbenzenesulfonic acid, 8 parts by weight of fatty alcohol polyglycol ether, 2 parts by weight of sodium salt of a phenol-urea-formaldehyde condensate and 68 parts by weight of a paraffinic mineral oil. A stable oily dispersion is obtained.

To widen the spectrum of action and to achieve a synergistic effect, the saccharincarboxylic acid derivatives I can be mixed with numerous representatives of other herbicidal or growth-regulating active compound groups and applied jointly. For example, suitable basic components are diazines, 4H-3,1-benzoxazine derivatives, benzothiadiazinones, 2,6-dinitroanilines, N-phenylcarbamates, thiocarbamates, halocarboxylic acids, triazines, amides, ureas, diphenyl ethers, triazinones, uracils, benzofuran derivatives, cyclohexane-1,3-dione derivatives which carry eg. a carboxyl or carbimino group in the 2-position, quinolinecarboxylic acid derivatives, imidazolinones, sulfonamides, sulfonylureas, aryloxy- or heteroaryloxyphenoxypropionic acids and their salts, esters and amides and others.

Additionally, it may be useful to apply the compounds I on their own or together in combination with other herbicides, additionally mixed with further crop protection agents, for example with agents for controlling pests or phytopathogenic fungi and bacteria. Further of interest is the miscibility with mineral salt solutions, which are employed for the elimination of nutritional and trace element deficiencies. Non-phytotoxic oils and oil concentrates can also be added.

PREPARATION EXAMPLES 1. 2-Methyl-6-acetamidobenzoic acid

90.6 g (0.6 mol) of 6-methylanthranilic acid are added to a solution of 24.8 g (0.62 mol) of NaOH in 500 ml of water and 63.4 g (0.62 mol) of acetic anhydride are then added dropwise. After stirring for one hour, the mixture is acidified to pH 3 with conc. HCl with cooling, and the precipitate which deposits is filtered off with suction, washed with water and dried under reduced pressure at 50° C. Yield: 107 g (0.55 mol)=92% of theory, m.p.: 189°-190° C.

2. 2-Methyl-3-nitro-6-acetamidobenzoic acid

271 ml of 98 percent nitric acid are initially taken at -5° C. and 106 g (0.55 mol) of the 2-methyl-6-acetamidobenzoic acid prepared in 1. are added in portions. After stirring at 10° C. for one hour, the reaction mixture is poured into a mixture of 540 g of ice and 270 ml of water. The deposited precipitate is filtered off with suction, washed with water and dried under reduced pressure at 50° C. Yield: 75.6 g (0.317 mol)=58% of theory, m.p.: 190°-191° C.

The isomer nitrated in the 3-position is deposited from the filtrate after relatively long standing: Yield: 21.3 g (0.089 mol)=16% of theory, m.p.: 180°-182° C.

3. 2-Methyl-3-nitro-6-aminobenzoic acid

450 ml of 2N NaOH are initially taken and 75.6 g (0.317 mol) of 2-methyl-3-nitro-6-acetamidobenzoic acid are added. The reaction mixture is then warmed to 95° C. and is stirred at this temperature for one hour. After cooling to 10° C., it is acidified by addition of 425 ml of 2N HCl, and the precipitate which deposits is filtered off with suction, washed with water and dried under reduced pressure at 50° C. Yield: 50.7 g (0.258 mol)=82% of theory, m.p.: 183°-184° C.

4. Methyl 2-methyl-3-nitro-6-aminobenzoate

49.7 g (0.253 mol) of 2-methyl-3-nitro-6-aminobenzoic acid are dissolved in 380 ml of acetone and 43 g (0.51 mol) of sodium hydrogen carbonate are added. The mixture is then heated to boiling until evolution of CO₂ is complete. 35.3 g (0.28 mol) of dimethyl sulfate are then added in the course of two hours at the boiling point of acetone to the suspension of the sodium salt of 2-methyl-3-nitro-6-aminobenzoic acid thus obtained, and the mixture is subsequently refluxed 30 for a further three hours and then allowed to cool. After pouring the reaction mixture into 1.8 l of water, it is extracted with methylene chloride. After drying the organic phase, it is concentrated. The solid obtained is sufficiently pure for the subsequent reaction (NMR). Yield: 50 g (0.238 mol)=94% of theory, m.p.: 92°-94° C.

5. 2-Methoxycarbonyl-3-methyl-4-nitrobenzenesulfonyl chloride

58.5 g (0.278 mol) of methyl 2-methyl-3-nitro-6-aminobenzoate 4O are dissolved with warming in 280 ml of glacial acetic acid and this solution is poured at from 15° to 20° C. into 85 ml of conc. HCl. A solution of 19.3 g (0.28 mol) of sodium nitrite in 60 ml of water is then added dropwise at from 5° to 10° C. and the mixture is stirred at 5° C. for 30 min. This diazonium salt solution is subsequently added dropwise to a solution of 374 g of SO₂ in 750 ml of glacial acetic acid which contains 14 g of CuCl₂ (dissolved in 30 ml of water). After completion of the evolution of nitrogen, the mixture is stirred for a further 15 min and then poured into 1.4 l of ice-water. The sulfonyl chloride is separated off by extraction with 1.2 l of methylene chloride. After drying and concentrating the organic phase, 73 g (0.25 mol) (=90% of theory) of an oil are obtained, which according to NMR (in CDCl₃) is pure 2-methoxycarbonyl-3-methyl-4-nitrobenzenesulfonyl chloride.

6. 4-Methyl-5-nitrosaccharin

104 ml of 25 percent ammonia solution are initially taken, 100 ml of water are added and a solution of 48.7 g (0.166 mol) of 2-methoxycarbonyl-3-methyl-4-nitrobenzenesulfonyl chloride in 70 ml of tetrahydrofuran is then added dropwise at 10° C. After stirring at 25° C. for three hours, water and THF are removed by concentration on a rotary evaporator, and the residue which remains is stirred with ethyl acetate, filtered off with suction and washed with ethyl acetate. After drying under reduced pressure, 34 g (0.131 mol)=79% of theory of a white solid of m.p.: 312° C. (dec.) are obtained.

7. 2,4-Dimethyl-5-nitrosaccharin

This substance can be prepared by subsequent methylation of the saccharin obtained in 6. using dimethyl sulfate in the presence of NaOH.

8. 3-Methyl-4-nitro-2-(N'-methyl)carboxamido-N-methylbenzenesulfonamide

50 ml of water are poured into 50 ml of 40 percent methylamine solution and a solution of 24.3 g (83 mmol) of 2-methoxycarbonyl-3-methyl-4-nitrobenzenesulfonyl chloride in 35 ml of THF is then added dropwise at 10° C. After stirring for one hour at 25° C., all volatile constituents are removed on a rotary evaporator. The residue is extracted with ethyl acetate, and the organic phase is washed with water, dried and concentrated. The residue which remains crystallizes after relatively long standing. Yield: 10.3 g (40 mmol=48% of theory), m.p.: 125°-126° C., after recrystallization from ethyl acetate m.p.: 144°-145° C.

According to NMR, the product is not a saccharin derivative but a carboxamide containing an additional sulfonamide group.

9. 4-Methyl-5-aminosaccharin

33.6 g (0.13 mol) of 4-methyl-5-nitrosaccharin are dissolved in 1.2 1 of water with warming and 5 g of Pd/C (10 percent on active carbon) are added. Hydrogen gas is then passed in with vigorous stirring (pressureless hydrogenation). 9 l of H₂ are absorbed in the course of 4.5 hours. After cooling to 25° C., the catalyst is filtered off, and the filtrate is concentrated on a Rotavapor to a volume of 200 ml and then acidified to pH 1. The deposited precipitate is filtered off with suction, washed with water and dried under reduced pressure at 50° C. 23.4 g (0.11 mol=85% of theory) of a white solid of m.p.: 272°-273° C. are obtained.

10. 4-Methyl-5-iodosaccharin

A mixture of 205 ml of glacial acetic acid, 160 ml of water and 40 ml of conc. HCl is initially taken and 23.4 g (0.11 mol) of 4-methyl-5-aminosaccharin are introduced with stirring at 15°-20° C. 7.9 g (0.115 mol) of sodium nitrite are added dropwise to the resulting suspension at 5°-10° C. and it is stirred at 5° C. for 30 min. The diazonium salt, which is present as a suspension, is then added dropwise in portions to a solution, which is warmed to 50° C., of 19.1 g (0.115 mol) of potassium iodide in 170 ml of water, nitrogen being formed. After cooling to room temperature, the deposited product is isolated by filtering off with suction, washed with water and dried under reduced pressure at 50° C. 32.5 g (0.1 mol=91% of theory) of a solid of m.p.: 257°-258° C. are obtained.

A combustion analysis gave an iodine content of 38.5% (theory 39.3%).

The product is sufficiently pure for the subsequent reactions.

11. 4-Methylsaccharin-5-carboxylic acid

6.4 g (0.002 mol) of 4-methyl-5-iodosaccharin are dissolved in 70 ml of tetramethylurea and 30 ml of water and treated with 0.7 g of bis(triphenylphosphine)palladium chloride and the mixture is heated to 100° C. in a 300 ml autoclave and stirred at a pressure of 100 bar of carbon monoxide for 36 h.

For working up, the mixture is filtered, and water and tetramethylurea are removed by distillation in a high vacuum. The residue is taken up in methyl tert-butyl ether (MTBE), extracted with NaHCO₃ soln. and, after acidifying with HCl, extracted again with MTBE. After concentrating, 2.8 g of 4-methylsaccharin-5-carboxylic acid (58% of theory) are obtained.

¹ H NMR (DMSO, 400.1 MHz): 2.85 (3H, s); 8.05 (1H, d); 8.2 (1H, d);

¹³ C NMR (DMSO, 100.6 MHz): 167.4 (CO); 161.3 (CO); 141.6 (quart. C); 139.7 (quart. C); 138.7 (quart. C); 135.6 (CH); 125.4 (quart. C); 118.5 (CH); 15.4 (CH₃).

12. 2,4-Dimethylsaccharin-5-carboxylic acid

7.3 g (0.02 mol) of 3-methyl-4-iodo-2-(N'-methyl)carboxamido-N-methylbenzenesulfonamide are initially taken in a 300 ml autoclave, together with 0.69 g of bis(triphenylphosphine)palladium chloride, 30 ml of water and 70 ml of tetramethylurea, and the mixture is heated to 100° C. and stirred at a pressure of 100 bar of carbon monoxide for 36 h.

After working up as described in Example 12, 4.1 g of the title compound 2,4-dimethyl-saccharin-5-carboxylic acid are obtained (0.014 mol=72% of theory).

¹ H NMR (DMSO, 400.1 MHz): 2.9 (3H, s); 3.15 (3H, s); 8.2 (2H, 2d); 14.0 (1H, s)

¹³ C NMR (DMSO, 100.6 MHz): 167.3 (CO); 158.6 (CO); 139.7 (quart. C); 139.1 (quart. C); 138.9 (quart. C); 135.5 (CH); 124.6 (quart. C); 119.0 (CH); 22.9 (CH₃); 15.6 (CH₃).

13. 4-Amino-3-methyl-2-(N'-methyl)carboxamido-N-methylbenzenesulfonamide

In a similar manner to the procedure described in section 9, the 3-methyl-4-nitro-2-(N'-methyl)carboxamido-N-methylbenzenesulfonamide obtained in section 8 is hydrogenated without pressure. An aniline derivative of the structure ##STR12## of m.p.: 217°-218° C. is obtained in 93% yield.

14. 3-Methyl-4-iodo-2-(N'-methyl)carboxamido-N-methylbenzenesulfonamide

The above compound is diazotized according to the procedure described in section 10 and converted to the iodobenzene derivative structure by reaction with KI. Yield: 95%, m.p.: 60°-62° C. ##STR13##

15. 2,4-Dimethylsaccharin-5-carbonyl chloride

3.8 g (14.9 mmol) of 2,4-dimethylsaccharin-5-carboxylic acid are suspended in 100 ml of toluene, and the fixture is heated to 80° C. and 3.5 g (29.8 mmol) of thionyl chloride are added dropwise. After refluxing for two hours, the solution is decanted hot and the reaction mixture is concentrated. The product obtained (3 g, 74% of theory) has m.p.: 149°-150° C.

16. General preparation procedure for the active compounds of the formula I

0.43 g (18 mmol) of magnesium turnings are added to a solution of 15 mmol of the respective cyano ketone of the formula A1 in 50 ml of methanol and 1 ml of CCl₄ is added dropwise at 25° C. After stirring for 2 hours, the methanol is stripped off under reduced pressure and the residue is dissolved in acetonitrile. A solution of 15 mmol of the saccharincarbonyl chloride of the formula III in 20 mi of acetonitrile is then added dropwise at 20°-25° C. and the mixture is stirred at 25° C. for 16 hours. For working up, the acetonitrile is first stripped off under reduced pressure, the residue is taken up in ethyl acetate and undissolved by-products are filtered off, and the solution is extracted by shaking with 50 ml of 10 percent HCl, then washed twice with water, dried over sodium sulfate and concentrated. The oily residue precipitates the product of the formula I as a crystalline solid on rubbing with cyclohexane.

The following active compounds in Table 1 can be obtained in the same way:

    ______________________________________                                          ##STR14##                                                                                                                M.p.                                No.  R.sup.1   Q position                                                                              L     M     Z      (°C.)                        ______________________________________                                         1.01 cyclo-C.sub.3 H.sub.5                                                                    4        H     H     H                                          1.02 cyclo-C.sub.3 H.sub.5                                                                    5        H     H     H                                          1.03 cyclo-C.sub.3 H.sub.5                                                                    6        H     H     CH.sub.3                                                                              >225                                1.04 cyclo-C.sub.3 H.sub.5                                                                    4        5-CH.sub.3                                                                           H     CH.sub.3                                   1.05 cyclo-C.sub.3 H.sub.5                                                                    5        H     4-CH.sub.3                                                                           C.sub.2 H.sub.5                            1.06 cyclo-C.sub.3 H.sub.5                                                                    5        4-Cl  H     CH.sub.3                                   1.07 cyclo-C.sub.3 H.sub.5                                                                    5        H     4-Cl  Propargyl                                  1.08 cyclo-C.sub.3 H.sub.5                                                                    6        H     4-CH.sub.3                                                                           CH.sub.3                                   1.09 cyclo-C.sub.3 H.sub.5                                                                    6        H     4-Cl  CH.sub.3                                   1.10 cyclo-C.sub.3 H.sub.5                                                                    6        5-Cl  H     C.sub.6 H.sub.5                            1.11 cyclo-C.sub.3 H.sub.5                                                                    6        5-CH.sub.3                                                                           H     C.sub.2 H.sub.5                            1.12 tert. C.sub.4 H.sub.9                                                                    4        5-CH.sub.3                                                                           H     CH.sub.3                                   1.13 tert. C.sub.4 H.sub.9                                                                    5        H     H     CH.sub.3                                   1.14 tert. C.sub.4 H.sub.9                                                                    5        H     4-Cl  Propargyl                                  1.15 tert. C.sub.4 H.sub.9                                                                    5        4-Cl  H     CH.sub.3                                   1.16 tert. C.sub.4 H.sub.9                                                                    6        H     H     H                                          1.17 tert. C.sub.4 H.sub.9                                                                    6        5-CH.sub.3                                                                           H     CH.sub.3                                   1.18 tert. C.sub.4 H.sub.9                                                                    6        H     7-Cl  H                                          1.19 tert. C.sub.4 H.sub.9                                                                    6        H     7-Cl  CH.sub.3                                   1.20 tert. C.sub.4 H.sub.9                                                                    6        5-CH.sub.3                                                                           H     C.sub.2 H.sub.5                            ______________________________________                                    

USE EXAMPLES

It was possible to show the herbicidal action of the saccharin derivatives of the formula I by greenhouse tests:

The cultivation vessels used were plastic flowerpots containing loamy sand with about 3.0% humus as a substrate. The seeds of the test plants were sown separately according to species.

In the case of preemergence treatment, the active compounds suspended or emulsified in water were applied directly after sowing by means of finely dispersing nozzles. The vessels were lightly watered in order to promote germination and growth, and then covered with transparent plastic hoods until the plants had taken root. This covering causes a uniform germination of the test plants if this is not adversely affected by the active compounds.

For the purpose of postemergence treatment, the test plants were first raised, according to growth form, to a height of growth of from 3 to 15 cm and only then treated with the active compounds suspended or emulsified in water. For this purpose, the test plants were either sown directly and raised in the same vessels or they were first raised separately as seed plants and transplanted into the test vessels a few days before the treatment.

The plants were kept species-specifically at from 10° to 25° C. or 20° to 35° C. The test period extended over 2 to 4 weeks. During this time, the plants were tended and their reaction to the individual treatments was assessed.

Rating was carried out on a scale of from 0 to 100. 100 in this case means no emergence of the plants or complete destruction of at least the above-ground parts and 0 means no damage or normal course of growth. 

We claim:
 1. A saccharin derivative of the formula I ##STR15## where the substituents have the following meanings: L and M are hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -alkylthio, chlorine, cyano, methylsulfonyl, nitro or trifluoromethyl;Z is hydrogen, C₁ -C₄ -alkyl, C₃ -C₈ -cycloalkyl, C₃ -C₆ -alkenyl, C₃ -C₅ -alkynyl, C₁ -C₄ -acyl, benzyl or phenyl, the phenyl rings being unsubstituted or substituted by halogen or C₁ -C₄ -alkyl; R¹ is cyclopropyl, 1-methylcyclopropyl, 1-methylthiocyclopropyl or tert-butyl;and agriculturally customary salts of the compounds I.
 2. A saccharin derivative of the formula I as claimed in claim 1, where Z is methyl, ethyl, propargyl or phenyl.
 3. A saccharin derivative of the formula I as claimed in claim 1, where the radicals L and M are hydrogen, methyl, methoxy, methylthio, chlorine, cyano, methylsulfonyl, nitro or trifluoromethyl.
 4. A herbicidal composition containing at least one saccharin derivative of the formula I as claimed in claim 1 and customary inert additives.
 5. A method of controlling undesired plant growth, which comprises applying a herbicidally active amount of a saccharin derivative of the formula I as claimed in claim 1 to the plants or their habitat.
 6. A process for preparing the compounds of the formula I as claimed in claim 1, which comprises converting cyano ketones of the formula A1 ##STR16## to their magnesium enolates and reacting these with an acid chloride of the formula III ##STR17## 